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/*
 *
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 *
 * Copyright (c) 2000 World Wide Web Consortium,
 * (Massachusetts Institute of Technology, Institut National de
 * Recherche en Informatique et en Automatique, Keio University). All
 * Rights Reserved. This program is distributed under the W3C's Software
 * Intellectual Property License. This program is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY; without even
 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.
 * See W3C License http://www.w3.org/Consortium/Legal/ for more details.
 */

package org.w3c.dom.traversal;

import org.w3c.dom.Node;
import org.w3c.dom.DOMException;

/**
 * <code>TreeWalker</code> objects are used to navigate a document tree or subtree using the view of
 * the document defined by their <code>whatToShow</code> flags and filter (if any). Any function
 * which performs navigation using a <code>TreeWalker</code> will automatically support any view
 * defined by a <code>TreeWalker</code>. <p>Omitting nodes from the logical view of a subtree can
 * result in a structure that is substantially different from the same subtree in the complete,
 * unfiltered document. Nodes that are siblings in the <code>TreeWalker</code> view may be children
 * of different, widely separated nodes in the original view. For instance, consider a
 * <code>NodeFilter</code> that skips all nodes except for Text nodes and the root node of a
 * document. In the logical view that results, all text nodes will be siblings and appear as direct
 * children of the root node, no matter how deeply nested the structure of the original document.
 * <p>See also the <a href='http://www.w3.org/TR/2000/REC-DOM-Level-2-Traversal-Range-20001113'>Document
 * Object Model (DOM) Level 2 Traversal and Range Specification</a>.
 *
 * @since DOM Level 2
 */
public interface TreeWalker {

  /**
   * The <code>root</code> node of the <code>TreeWalker</code>, as specified
   * when it was created.
   */
  public Node getRoot();

  /**
   * This attribute determines which node types are presented via the
   * <code>TreeWalker</code>. The available set of constants is defined in
   * the <code>NodeFilter</code> interface.  Nodes not accepted by
   * <code>whatToShow</code> will be skipped, but their children may still
   * be considered. Note that this skip takes precedence over the filter,
   * if any.
   */
  public int getWhatToShow();

  /**
   * The filter used to screen nodes.
   */
  public NodeFilter getFilter();

  /**
   * The value of this flag determines whether the children of entity
   * reference nodes are visible to the <code>TreeWalker</code>. If false,
   * these children  and their descendants will be rejected. Note that
   * this rejection takes precedence over <code>whatToShow</code> and the
   * filter, if any.
   * <br> To produce a view of the document that has entity references
   * expanded and does not expose the entity reference node itself, use
   * the <code>whatToShow</code> flags to hide the entity reference node
   * and set <code>expandEntityReferences</code> to true when creating the
   * <code>TreeWalker</code>. To produce a view of the document that has
   * entity reference nodes but no entity expansion, use the
   * <code>whatToShow</code> flags to show the entity reference node and
   * set <code>expandEntityReferences</code> to false.
   */
  public boolean getExpandEntityReferences();

  /**
   * The node at which the <code>TreeWalker</code> is currently positioned.
   * <br>Alterations to the DOM tree may cause the current node to no longer
   * be accepted by the <code>TreeWalker</code>'s associated filter.
   * <code>currentNode</code> may also be explicitly set to any node,
   * whether or not it is within the subtree specified by the
   * <code>root</code> node or would be accepted by the filter and
   * <code>whatToShow</code> flags. Further traversal occurs relative to
   * <code>currentNode</code> even if it is not part of the current view,
   * by applying the filters in the requested direction; if no traversal
   * is possible, <code>currentNode</code> is not changed.
   */
  public Node getCurrentNode();

  /**
   * The node at which the <code>TreeWalker</code> is currently positioned.
   * <br>Alterations to the DOM tree may cause the current node to no longer
   * be accepted by the <code>TreeWalker</code>'s associated filter.
   * <code>currentNode</code> may also be explicitly set to any node,
   * whether or not it is within the subtree specified by the
   * <code>root</code> node or would be accepted by the filter and
   * <code>whatToShow</code> flags. Further traversal occurs relative to
   * <code>currentNode</code> even if it is not part of the current view,
   * by applying the filters in the requested direction; if no traversal
   * is possible, <code>currentNode</code> is not changed.
   *
   * @throws DOMException NOT_SUPPORTED_ERR: Raised if an attempt is made to set
   * <code>currentNode</code> to <code>null</code>.
   */
  public void setCurrentNode(Node currentNode)
      throws DOMException;

  /**
   * Moves to and returns the closest visible ancestor node of the current
   * node. If the search for <code>parentNode</code> attempts to step
   * upward from the <code>TreeWalker</code>'s <code>root</code> node, or
   * if it fails to find a visible ancestor node, this method retains the
   * current position and returns <code>null</code>.
   *
   * @return The new parent node, or <code>null</code> if the current node has no parent  in the
   * <code>TreeWalker</code>'s logical view.
   */
  public Node parentNode();

  /**
   * Moves the <code>TreeWalker</code> to the first visible child of the
   * current node, and returns the new node. If the current node has no
   * visible children, returns <code>null</code>, and retains the current
   * node.
   *
   * @return The new node, or <code>null</code> if the current node has no visible children  in the
   * <code>TreeWalker</code>'s logical view.
   */
  public Node firstChild();

  /**
   * Moves the <code>TreeWalker</code> to the last visible child of the
   * current node, and returns the new node. If the current node has no
   * visible children, returns <code>null</code>, and retains the current
   * node.
   *
   * @return The new node, or <code>null</code> if the current node has no children  in the
   * <code>TreeWalker</code>'s logical view.
   */
  public Node lastChild();

  /**
   * Moves the <code>TreeWalker</code> to the previous sibling of the
   * current node, and returns the new node. If the current node has no
   * visible previous sibling, returns <code>null</code>, and retains the
   * current node.
   *
   * @return The new node, or <code>null</code> if the current node has no previous sibling.  in the
   * <code>TreeWalker</code>'s logical view.
   */
  public Node previousSibling();

  /**
   * Moves the <code>TreeWalker</code> to the next sibling of the current
   * node, and returns the new node. If the current node has no visible
   * next sibling, returns <code>null</code>, and retains the current node.
   *
   * @return The new node, or <code>null</code> if the current node has no next sibling.  in the
   * <code>TreeWalker</code>'s logical view.
   */
  public Node nextSibling();

  /**
   * Moves the <code>TreeWalker</code> to the previous visible node in
   * document order relative to the current node, and returns the new
   * node. If the current node has no previous node,  or if the search for
   * <code>previousNode</code> attempts to step upward from the
   * <code>TreeWalker</code>'s <code>root</code> node,  returns
   * <code>null</code>, and retains the current node.
   *
   * @return The new node, or <code>null</code> if the current node has no previous node  in the
   * <code>TreeWalker</code>'s logical view.
   */
  public Node previousNode();

  /**
   * Moves the <code>TreeWalker</code> to the next visible node in document
   * order relative to the current node, and returns the new node. If the
   * current node has no next node, or if the search for nextNode attempts
   * to step upward from the <code>TreeWalker</code>'s <code>root</code>
   * node, returns <code>null</code>, and retains the current node.
   *
   * @return The new node, or <code>null</code> if the current node has no next node  in the
   * <code>TreeWalker</code>'s logical view.
   */
  public Node nextNode();

}
